The present invention relates to a power transfer device employed in a four-wheel drive vehicle such as a vehicle for construction, a wheel loader, a wheel crane and a jeep.
Conventionally, some of the such vehicles have employed sub-transmissions for compensating gear ratios of main transmissions and selector mechanisms for selecting four-wheel driving and two-wheel driving. Further, differential mechanisms are arranged for distributing power to front wheel axles and rear wheel axles. On a rough land, the vehicle can run in the four-wheel drive condition, and the sub-transmission is set in a low gear range. When tires may slip at a high gear range, the differential is set in a lock condition (non-operation condition). When the tires may not slip, the differential is set in an operation condition. In the high gear range, two-wheel driving can be performed to improve fuel consumption. As stated above, the above-mentioned vehicle has such an advantage that the driving conditions can be selected preferably in accordance with the running condition.
However, in the conventional device, said various mechanisms are arranged indipendently to each other, which results in such a disadvantage that the whole mechanisms have large and complicated structures and are expensive. Further, there is such a disadvantage in the conventional device that an operating mechanism is also complicated, and thus, manual operation can not be simple.
Accordingly, it is an object of the invention to provide an improved power transfer device, overcoming the above-noted disadvantages, wherein a differential mechanism can be used also as a transmission mechanism.
According to the invention, the power transfer device for a vehicle comprising a power input part; an intermediate gear mechanism having an intermediate input gear supported by the power input part and an intermediate output gear meshing with the intermediate input gear; a first gear forming a first output part and meshing with the intermediate input gear; a first shaft connected to the first gear; a second output part adapted to be connected to the intermediate output gear; a second shaft connected to the second output part; a first auxiliary output part connected to the first shaft; a dog clutch disposed among the intermediate output gear, the first auxiliary output part and the second output part and being adapted to be switched between a differential operation position in which the intermediate output gear is connected only to the second output part and a differential non-operation position in which the intermediate output gear is connected to both of the first auxiliary output part and the second output part; a lock gear mechanism connected to the intermediate gear mechanism; and a lock mechanism adapted to disengagably connect the lock gear mechanism to a stationary part.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.